Variable-voltage transformer



Dec. 2, 1930.v

.1.A F. PETERS Fl' AL VARIABLE VOLTAGE TRANSFORMER Filed Feb. 2o, 192s Petenied Deeuz, 1930 UNITED `s'r-Afrlas P'TENT oFFle-n l JOHN F. PETERS AND J. ASLIN, OxEDGEWOOD, PENNSYLVANIA, ASSIGNOBS TO WESTINGBOUSE ELECTRIC AND yIIIANUFACT'U'BING' COMPANY, A. CORPORATION F PENNSYLVANIA VARIABLE-VOLTAGE 'rmsrommn l I Our invention relates to electrical translating devices and particularly vto transformers for deliverin testing instruments. ne object of our invention is to provide a transformer that shall bel capable of'delivering a variable voltage over a wide range. f

. Another object .of our invention is to provide a transformer for testing instruments l such that an operator may closely regulate the terminal `voltage thereof. i

A further object of our invention is to pro- V vide a transformer for delivering a variable voltage to testing instruments suchA that the operator may vary the applied voltage by a l -very large number of graduations as distinguished from a succession of relatively Ifew predetermined steps. i f Y lIn electrical testing and measuring appa- 29 ratus it is frequently necessary to employ the same instruments for-widely different cal culations and when such calculations depend upon voltage as a factor, it becomesnecessary that adtransformer shall be capable of developing a continuously varyingvoltage ratio, the characteristic curve of which is much smoot er thanthat obtained by vary-` ing the tap connections of one of the transformer windings through a succession of pre- 9 determined steps. e

`We obtain the foregoing results by employing a plurality of auxiliary windings, one of which is wound on 'the same core vleg as These auxiliary windings areconnectedto a common variable burden so that it isnpossible to short-circuit eitherone of thex auxiliary l 'windings or'to cause it to carry the entire variable-burden.' Accordingly, as the load on o the auxiliary coil that is mounted adjacent to the secondarycoil varies, 'the energization, and consequently the voltage output, of the secondary coil varies proportionally. In the accompanying drawings, v '-15 Fig. 1 is a diagrammatic view of a transformer and circuits embodying our invention. Fig. 2 `is asimilar view of a modifiedy forni ofaour invention. t

OurLinvention comprises, in general, a core member 1 ,having the customary privariable voltage to Atact element 8 adapted to selectively divide one of the windings of the secondary circuit. e

is moved to the left or the-right along the Appieatien ,mea rebruary'ao, 1a'2.e. serial No. 89,775.

mary winding 2 and secondarywinding B,

together with a pair of auxiliary windings 4 and 5 that are connected t a common variable burden such,'for example, as avariableA reslstor 6 and a measuring instrument' 7. 55

The auxiliary windings 4 and 5 are mounted upon different legs of the transformer than 1s the primary winding 2. The auxiliary winding 4, however, is mounted on the /same -i core leg as is the secondary winding v3. v The variable resistor 6 may be connected wholly or partially in series with either of the auxiliary windings 4 and 5 by an adjustable conthe resistor 6 into sub-divisions that are in serles respectively with the auxiliary coils 4 and 5.

The measuring instrument 7 which is pref;

erably a volt-meter, isconnected across the terminals of vthe Kauxiliary winding 4 'and may be calibrated to indicate the voltage acrossl the secondary coil 3.

Upon enrgization of the primary winding 2 and with the adjustable Contact in the mid-portion of the variable resistor 6, the ilu-x threading the auxiliary winding 5 and that threading the. auxiliary qwinding 4 and the auxiliary winding 3 are-inversely proportionalr to their relative impedances. Since the impedances of the'windings 4 and 5 are substantially equal, the winding 5 will be l threaded by enough more iux than the winding 4 to compehsate for the impedance of the secondary wlnding 3 witlrthe result that the voltage across the'auxiliary winding 5 will;85

be slightly in excess of that acrbss the auxiliary winding 4 and Ithereading on the inf strument 7 represents the difference in otential across the terminals of the win ing 4 which difference in potential is directly proportional to the potential across the second-d ary windin 3.

t is obvious that, as the movable contactor variable resistor 6, the impedances of the coils ,95

v4 and 5 vary correspondingly with the result that the readings of the instrument 7 likewise vary in accordance with the potential of the secondaryrwinding 3. `Assuming, the movable contact member tofbe attheextreme I' left hand terminal-.of the variable resistor 6,

the auxiliary winding 4 will be short-circuited and its impedance will be such as to precludeJan'y ux traversing that leg of the transformer core 1 with the result that the voltage" across the terminalsof the secondary winding 3v-is zero. At the same time, all of the iiux generated by4 the primary. winding 2 threads the auxiliary winding 5.

As the contact member 8 is moved along the variable resistor 6 to the right, the combined impedances of the auxiliary winding 4 and the secondary winding 3 decrease, an appreciable voltage appears across their terminals which is registered by the measuring instrument 7 L This voltage increases until the contact memberS is moved to the extreme right of the variable resistor 6 when the impedance of the auxiliary winding 5 becomes so lowas topreclude the passage of any-lux therethrough, at which time allthe flux traverses the windings 3 and 4. Under such conditions, the instrument 7 registers its maximum reading and the secondary winding 3 delivers its maximum voltage. v

` Referring -particularly to Fig. 2, we have shown a modified form of our invention in which the secondary vcoil is divided into two sections 11 and 12, section 12 being mounted on the same legas is the primary winding 2,

while the section 11 is mounted on the same leg as is the auxiliary winding 4. By placing a reversing switch 13 across the terminals of one of the sections 12 or 13 so that they either oppose or assist each other, it is possible to secure a voltage across the secondary winding of the transformer that varies over a range I y of voltage proportional to the sum of the volttion is similar to the interaction between the .secondary winding 3 and the secondary winding 4 in the form of our invention shown in .F1g. 1. l

In the form of our invention shown in Fig.

2 the section 12 of the secondary winding will normally deliver its full potential by reason of its being mounted on the same core leg as the primarywinding 2 while the voltage delivered by the secondary winding 11 varies from zei'o to its maximum, in accordance with the positlon of the adjustable contact member 8 with referencerto the variable burden 6.v

This maximum potential of the section l1 may oppose or be additive'to the potential of the section 12.

In both forms of our invention the auxiliary winding 5 is mounted alone on one of the legs of the core member l.

It will thus be seen that we have provided a transformer for delivering a continuous but variable voltage for testing and measur- 'ing instruments that is characterized by employing an auxiliary winding to control the uxtraversing it and a secondary winding and thereby vary the potential of the 'secondary winding.

It is to be understood that such changes may be made in the arrangement and disposiltion of the several parts of our invention as connected to the auxiliary windings for coni 4 trolling the flux distribution between the several legs associated with the auxiliary wind- 1ngs. Y

2. In a transformer, a core member com'- prising a plurality of legs, a primary coil mounted on oneof the legs, a secondary winding mounted at least partially on a second leg, and auxiliary windings on certain of the transformer legs, one of the auxiliary windings being mounted on said second leg and adjustable means connected to the auxiliary windings for controlling the flux distribution in the several transformer legs.

3. In a transformer, a core member comprising a plurality of legs, a primary coil mounted on one of the legs, a secondary winding mounted at least partially on a'second leg, and auxiliary windings on certain of the transformer legs, one of the auxiliary windings being mounted on said second leg, and a variable burden connected to the auxiliary windings causing the auxiliary winding associated with the secondary winding to operate between conditions of short-circuit and full burden whereby the voltage delivered by the secondary winding is varied.

4. In a transformer, a core, a' primary winding thereon, an auxiliary winding and a secondary winding mounted on the same core leg, and means for varying the reactance of the auxiliary winding comprising a variable burden and an auxiliary winding mountedon another core leg and connected in circuit with the first-named auxiliary winding and the variable burden for controlling the reactance of the first named auxiliary coil and thereby the voltage of the secondary winding.

5. In a transformer, a core structure, primary and secondary windings associated therewith, an auxiliary circuit comprising a pluralit of windings mounted on dii'erent legs of t e core structure, and means for propertioning the ux traversing the respective last-named windingsf I v 6; In a transformer, a core structure, a primary Winding on one core leg, a secondary winding on another core leg-two aum'l`v iary windings on separate core legs, and ay burden in circuitl with said auxiliary Windvim? ings for inversely varying the impedance of vsaid auxiliary windings. '7. ln a transformer, a core structure, a

primary Winding on one core leg, a secondary Winding on another core leg, aumliary windings onseparate core legs, a burden in circuit with said auxiliary windings, and l means for controlling the impedances of said `auxiliary windings.

8. lin a transformer, a' core structure, a primary Winding von one core leg, a secondary Winding on another eore'leg, an auxiliary winding on said other core leg, an auxiliary Winding on another core leg, and a burden in circuit with said auxiliary windings.

9. In a transformer, a core structure hav;

ing a plurality of core legs, "a primary Windling on one core leg, a secondary winding and an auxiliaryvvinding on. another core leg,

a second auxiliary Winding on another core leg and a variable burden in circuit with said auxiliary windings for controlling the flux traversing said windings.

In testimony whereof, We have hereunto subscribed our names this 26th day of J anuary, 1926.

JOHN F. PETERS. ALBERT J. MASLIN. 

